A fiber-optic sensor for monitoring of duodenogastric reflux is fabricated. The sensing system, based on the principle of double-beam compensation, includes two diodes for light sources, blue at 470 nm as signal light and yellow at the wavelength of 595 nm as reference one, and a Y model fiber optic bundle for transmitting light. The sensor performs on detection of spectrophotometric absorption of bilirubin always present in entero-gastric reflux at 470 nm and 595 nm. A general evaluation of the sensor about factors affecting its detection is discussed in detail: Wavelength choice, pH, scattering effect resulting from gastric precipitates and others. The sensor shows a good excellent performance with a dynamic linear range of up to 10 mg/dl. The in-vitro experiment shows it can be used in clinical analysis of DGR